In the present day, beamline ion implanters employ multiple components to direct an ion beam from an ion source to a substrate. In order to properly treat a substrate, the ion beam may be accelerated or decelerated to a target ion energy, and may have the trajectory and shape of the ion beam manipulated by various beamline components to produce a set of target characteristics of the ion beam at the substrate. In many types of ion implanters, including medium energy and low energy ion implanters, an ion source may generate an ion beam that is guided down a beamline at a relatively high energy, while decelerated to a final energy just before impacting a substrate. This procedure is used because a best way to produce high current beams (having current more than ≈1 mA) at low energy (under ≈10 keV) is to transport an ion beam at a relatively higher energy through ion extraction, mass analysis and other beamline elements, before deceleration takes place to a final energy at the latest possible stage before striking the substrate. Such low energy high current beams will not transport for long distances in a beamline because of space charge forces that cause the ions to repel one another. In known ion implanters, the architecture with deceleration near the wafer introduces a risk of energy contamination from energetic species that strike the substrate. In particular, ions that are neutralized in the volume just before or during a final deceleration will continue to propagate with no change in energy, and may accordingly strike the wafer (substrate) at a higher energy than intended.
In some ion implanters, this problem is addressed by providing a bend within a component such as a deceleration stage so that neutrals traveling through the deceleration stage may be screened from the substrate by virtue of the bend in the deceleration stage. While neutrals traveling in a straight direction may fail to reach the substrate, energy contamination is found even in ion implanters having a bend in a deceleration stage.
With respect to these and other considerations the present disclosure is provided.